Women who use permanent hair dyes at least once a month increase their risk of contracting bladder cancer 2.1 times compared to non-users, according to a study conducted by Manuela Gago-Dominguez, et al., University of Southern California.

Published in the February edition of the International Journal of Cancer, the study found risk of bladder cancer increases 3.3 times among monthly users of 15 or more years.

Occupational exposure to hair dyes in hairdressers or barbers who worked for more than 10 years resulted in a five-fold increase in risk.

The use of semi-permanent hair dyes and color rinses produced no significant statistical impact on bladder cancer risk, the study concludes.

"Highest risk was observed among those with the highest frequency and duration of use of permanent hair dyes," the researchers say.

The deleterious effects of permanent hair dye use were limited to women, as only 14 male cases and 16 male control subjects who regularly used permanent hair dyes participated in the study.

"The lack of exposure-disease association among our male subjects is likely the result of low exposure rate leading to low study power to detect the anticipated association," the study says.

However, in Europe, North America and Japan, it is estimated that more than one-third of women over 18 and 10% of men over 40 use "some type of hair dye," the study claims. In addition, about 2 mil. professional hairdressers are regularly exposed to hair dyes in North America and Europe.

The population-based, case-control study conducted in Los Angeles relied on information obtained from 897 subjects and their matched controls. Gago-Dominguez et al. estimate 19% of bladder cancer diagnosed in Los Angeles County is attributable to long-term permanent hair dye use.

Sampled cancer patients were between the ages of 25 and 64 with a mean age of 56.2. Most of the participants were Caucasian, with a smaller percentage of Hispanics, African-Americans and Native Americans rounding out the group.

Patients were paired with a control matched as closely as possible by sex, date of birth to within five years, ethnicity and neighborhood of residence at the time the cancer was diagnosed.

Subjects were questioned on the four-year period bracketing the cancer diagnosis and were asked to answer questions on demographic and physical characteristics, tobacco and alcohol use, dietary habits, lifetime occupational history, medical history and hair dye use.

Data were analyzed by standard matched pair methods with adjustments made for cigarette smoking, which is the most established risk factor for bladder cancer, according to the study.

The odds ratio examined in the study was more positive for non-smokers than for habitual smokers, who were almost twice as likely to contract bladder cancer compared with non-smokers, the researchers note.

The findings differ from two prior studies examining the relationship between exposure to permanent hair dyes and bladder cancer risk, according to Gago-Dominguez et al.

No increase in risk was observed in a cohort investigation involving 37 cases of urinary tract cancer or in an American Cancer Society investigation with an end point of fatal bladder cancer. The USC authors attribute the disparity to the "considerably larger" size of the more recent study.

The Cosmetics, Toiletry and Fragrance Association disagrees with the USC findings, pointing to the lack of significantly statistical data found in prior studies.

"There are many questions regarding the interpretation of this study, and it draws conclusions that are not supported by the data in the study," CTFA said in a statement Jan. 25.

"Hair dyes are one of the most thoroughly studied consumer products on the market today," CTFA stated. "They are safe and consumers can have great confidence in these products." CTFA is collaborating with outside experts to review the report.

Bladder cancer accounts for 6% of new cancer cases in men and 2% in women, according to the study.

Hair Dyes Increase Risk Of Bladder Cancer - USC Researchers

More from Archive

More from HBW Insight